Heat produces analgesia through recognized physiologic mechanisms including stimulation of thermal receptors that inhibit nociception via the gate-control theory, by increasing blood flow, and by reducing muscular spasm. Similarly transcutaneous electrical nerve stimulators (TENS) reduce pain by electrically "blocking" pain impulses via gating of nociception. Phase I created an innovative battery operated heating device that optimized the interaction with recognized heat pathways to increase analgesic effectiveness. A control unit connected to small heating pads allowed precise management of variables such as maximum temperature of the heating pad, rate of temperature rise, and depth and duration of heating cycles. Phase I hypothesized that activation of two separate afferent "gating" pathways, c-fiber dependent thermo-receptor from heat and deep tissue large diameter A-beta primary afferents from TENS would produce more analgesia than either heat or TENS used separately. We further hypothesized that heat alone would be as effective as TENS alone in providing pain relief. In phase I, both hypotheses were supported in a randomized controlled clinical trial. Commercialization was advanced through the filing of patents and successful completion of the NIH Commercialization Assistance Program (CAP). Phase II will create a smaller, more user-friendly device and several types of heating elements that allow treatment of separate areas of the body, and test two hypotheses. The first hypotheses is that the higher temperature and cyclic heat supplied by the study device will be preferred to that of the low level steady heat supplied by a commercially available device, Thermacare (Procter & Gamble). It is thought that the study device will produce stronger stimulation of thermal receptors than that produced by low-level chemical heating pads. The second trial determines if the device, when added to TENS will improve pain and function in a long-term study of patients with chronic low back pain. The second hypothesis is that heat will increase the effectiveness of TENS as compared to TENS alone in a long-term randomized trial that uses both self-rating of pain and functional outcomes as endpoints. This study will parallel a classic TENS study by Deyo et al. published in 1990 in the New England Journal of Medicine. This will be tested in a separate clinical trial. Finally, we will pursue commercialization of the device through contacts made in the NIH-Commercialization Assistance Program. [unreadable] [unreadable] [unreadable]